1. Field of the Invention
Implementations of various technologies described herein generally relate to seismic data processing, and more particularly, simulating up-going pressure wavefield data using pressure and particle velocity data acquired from over/under streamers.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Seismic exploration is widely used to locate and/or survey subterranean geological formations for hydrocarbon deposits. Since many commercially valuable hydrocarbon deposits are located beneath bodies of water, various types of marine seismic surveys have been developed. In a typical marine seismic survey, seismic streamers are towed behind a survey vessel. The seismic streamers may be several thousand meters long and contain a large number of sensors, such as hydrophones, geophones, and associated electronic equipment, which are distributed along the length of the seismic streamer cable. The survey vessel may also include one or more seismic sources, such as air guns and the like.
As the seismic streamers are towed behind the survey vessel, acoustic signals, commonly referred to as “shots,” produced by the one or more seismic sources are directed down through the water into strata beneath the water bottom, where they are reflected from the various subterranean geological formations. Reflected signals are received by the sensors, digitized, and then transmitted to the survey vessel. The digitized signals are referred to as “traces” and are recorded and at least partially processed by a signal processing unit deployed on the survey vessel. The ultimate aim of this process is to build up a representation of the subterranean geological formations beneath the streamers. Analysis of the representation may indicate probable locations of hydrocarbon deposits in the subterranean geological formations.
The seismic streamers may be in an over/under configuration, i.e., one set of streamers being suspended above another set of streamers. Streamers in an over/under configuration may be towed much deeper than streamers in a conventional single configuration.
Conventional techniques for simulating the up-going pressure wavefield data acquired by streamers in a twin over/under configuration generally involve a linear combination of pressure and particle velocity data. The linear combination may be deemed to be sufficient to create the up-going pressure wavefield free of sea-surface perturbations with an optimum overall signal-to-noise ratio, when the signal-to-noise ratio of the pressure data is significantly similar to that of the particle velocity data. If the signal-to-noise ratio of the pressure data differs significantly from that of the particle velocity data, the resulting up-going wavefield data may consist of an up-going wavefield without sea-surface perturbations but with a sub-optimum signal-to-noise ratio, or it may include an up-going wavefield with sea-surface perturbations but with an optimized the signal-to-noise ratio.